Study On Rainfall Erosive Force In Fang County Region Of Northwest Hubei Province

The Chinese investigation of soil erosion reported that the Slope Cropland and hydraulic erosion were the main reasons of soil erosion in 2004. At present, the exact prediction of soil erosion on Slope Cropland is very important. USLE can predict the soil erosion, and it has been widely application worldly. However, the factors in this equation must be corrected, and the rainfall erosion factors with the time and space variation are more complicated especially. The purpose of this study is to show the effect of rainfall in Northwest Hubei Province to the soil erosion on Slope Cropland, and attain the rainfall erosion in Fang county areas.The 14 runoff plots were begun to built in horticultural house in Fang county in April 2002, and the standard plots are Long ? Slope for 20 ? 5 meter, with 15°- slope. It has collected the data of rainfall and amount of soil loss from 2003 to 2005. It analyzed the relationship between the characteristics of rainfall and soil erosion and the relationship of the soil erosion variation with the different slopes, engineering Measures, and under layer Condition. The optimal raindrop kinetic energy formula was selected according to the present raindrop kinetic energy formulas for no formulas of this area. The simple formula of rainfall erosivity factors R value and secondary R value were got though selecting the relationship between E_mI_n and soil erosion, and the rainfall characters.It was indicted that the erosive rainfall amount in the standard plot was 14.6mm and selected the optimal unit kinetic energy formula as the common rainfall kinetic energy formula in northwest in Fang county area. The rainfall erosivity index ∑EI₁₀ was got according to the formula. The relationship between the R index and kinetic energy was also got by making use of the relationship between the total rainfall kinetic energy and average total kinetic energy (easily calculated)- ∑E = 1.103E_{平均}+9.991. And the total rainfall kinetic energy formula ∑E = 16.745P-23.021 in this area can be calculated by them when the rainfall account and the intensities of rainfall are known. The simple formula of secondary rainfall R={1.10·[ (11.55·logI_{平均}+27.83) ·P]+9.99}·I₁₀ can be calculated and tested by the average total kinetic energy get a formula according to the present data. This paper provides the value basis for the soil erosion prediction of slope cropland in Fang county area.